The invention relates to rotating seals for centrifugal devices useful, inter alia, in cell processing or cell washing applications.
Generally, cell processing requires steps in which cells or cell elements are separated from a liquid phase. This separation is typically accomplished by centrifugation. The sterility of the cells being processed is protected by the incorporation of a dynamic seal between rotatable and stationary centrifuge elements, referred to as a xe2x80x9crotating sealxe2x80x9d. In addition to deterring the entrance of microbes into the sterile environment of the processing apparatus and the biological materials contained therein, a rotating seal ideally minimizes the leakage of air and frictional heating and is capable of tolerating mild to moderate misalignment and vibration.
A number of designs for rotating seals have been developed. For example, U.S. Pat. No. 3,489,145 by Judson et al. discloses a lower rotating element that forms a seal with an upper stationary element, and that has a central bore extending throughout. U.S. Pat. Nos. 3,409,203 and 3,565,330 by Latham disclose rotating seals formed from a stationary rigid low-friction element in contact with a moving rigid element and an elastomeric element which provides a resilient static seal as well as a modest closing force between the seal surfaces. U.S. Pat. No. 3,801,142 by Jones et al. relates to a pair of elements having confronting annular fluid-tight sealing surfaces maintained in a rotatable but fluid-tight relationship by axial compression of a length of elastic tubing. In the xe2x80x9cB. T. Bowlxe2x80x9d marketed by Bellco (Mirandola, Italy), a rotating seal is formed between a ceramic ring element attached to rotatable elements of a centrifuge and a fixed graphite ring attached to stationary centrifuge elements; an elastomeric diaphragm is attached at one end to an adapter ring for the graphite ring and at the other end to a stationary part of the centrifuge. U.S. Pat. Nos. 4,300,717 and 5,045,048 by Latham, Jr. relate to a rotating seal which has been modified by the incorporation of recessed areas contiguous with xe2x80x9csealedxe2x80x9d regions; the recessed areas are in communication with the external environment and are used to entrap and expel extraneous particles which may form during centrifugation.
In the field of centrifugal cell washing, two technologies currently dominate the state of the art, as exemplified by the Cobe 2991 and the Haemonetics Model 115 cell washers. Both systems employ a set of rotating seals to contain the fluids in the disposable rotating containers. These seals have been classified by the FDA as xe2x80x9copenxe2x80x9d devices for the purpose of washing red blood cells, in that the seals have not yet been validated as having the ability to satisfactorily prevent biological contamination of the sterile interior under all running and handling conditions. According to the American Association of Blood Banks (xe2x80x9cAABBxe2x80x9d) standards, xe2x80x9cwhen glycerolizing or deglycerolizing involves entering the container, the system is considered xe2x80x98openxe2x80x99 and the resulting suspension of deglycerolized cells can be stored for only 24 hours at 1-6 degrees Centigrade.xe2x80x9d This 24-hour storage shelf life after deglycerolization, and other factors (including cost), make the foregoing systems less useful for routine inventory management and relegate them primarily to specialty uses such as storing rare blood types, autologous donations, or battlefield applications for the Navy.
None of the foregoing rotating seals provides a seal which permits the storage of processed biological materials such as red blood cells for extended period of time. The foregoing seals do not provide adequate protection from the contamination of processed biological materials by microbial contaminants.
The invention provides an improved rotating seal which provides enhanced anticontamination properties for use in particular in centrifugal devices for processing biological materials. The seal of the invention comprises at least two concentrically spaced rotating seals, wherein the annular space between the seals forms at least one sterile chamber. In the event of a leak in one of the concentrically spaced rotating seals, the additional seal or seals act to maintain the sterile environment of the cell processing system by reducing or preventing microbial contamination. In addition, the sterile annular chamber can be pressurized with a sterile supply of gas as a second means of reducing or preventing microbial contamination. The pressurized chamber acts as a barrier to prevent microbes from migrating into the interior of the cell processing system across a leaky seal. The pressurized chamber also acts as a barrier to reduce or prevent the migration of fluids or particulate matter from the interior of the cell processing system across the a leaky seal.
According to one aspect of the invention, an improved cell processing system is provided, the improvement comprising a plurality of annular rotating seals between rotating and non-rotating portions of the cell processing system. The plurality of annular rotating seals define at least one annular space between the annular rotating seals. The at least one annular space is constructed and arranged for receiving pressurized gas. In some embodiments, the plurality of annular rotating seals includes a plurality of sealing members defining annular sealing surfaces which form a plurality of concentrically spaced annular rotating seals, the annular rotating seals defining at least one annular space. At least one of the sealing members defines a channel in a non-sealing surface, which channel is in gaseous communication with the at least one annular space. Preferably the at least one annular space is pressurized with gas. In certain preferred embodiments, the annular sealing surfaces are substantially planar. In other embodiments, the apparatus also includes a body defining a gas port, wherein the gas port is in gaseous communication with the channel. The apparatus also can include a pressure sensor in communication with the gas port for monitoring the gas pressure in the annular space.
According to another aspect of the invention, a seal apparatus is provided. The seal includes plurality of annular seal members. A first annular rotating seal member includes a sealing face which defines a plurality of concentrically spaced annular sealing surfaces, and an axial opening. A second annular rotating seal member has a sealing face which defines at least one annular sealing surface, and an axial opening. The first annular rotating seal member and the second annular rotating seal member are axially aligned and the annular sealing surfaces are placed in contact to form a plurality of spaced apart seals. Preferably the annular sealing surfaces are substantially planar. In certain embodiments, the sealing face of the first sealing element further defines an annular space between the annular sealing faces. The annular sealing surfaces can be biased together by a bias element, which preferably is an elastomeric spring element. The annular sealing surfaces are preferably formed of a material selected from the group consisting of ceramics, carbon phenolic and equivalent carbon composite materials; more preferably, all annular sealing surfaces are formed of ceramic materials. In other embodiments, at least one of the non-sealing faces of the first annular rotating seal member and the second annular rotating seal member define a channel in gaseous communication with the annular space.
The seal apparatus also can include a body which includes a first port disposed in the axial openings of the first and second annular rotating seal members. Preferably at least one of the non sealing faces of the first annular rotating seal member and the second annular rotating seal member define a channel in gaseous communication with the annular space, wherein the body includes a gas port in communication with the channel. The seal apparatus also includes in some embodiments a base having an axial opening and a processing container having a top defining an axial opening. The base is mounted in axial alignment on the top of the processing container, and the second annular rotating seal member mounted in axial alignment on the top surface of the base. Thus assembled, the first port of the seal apparatus is in fluid communication with the interior of the processing container. Preferably the first port extends through the axial openings of the first and second annular rotating seal members and the base. The body also can include a fluid port in fluid communication with the space defined by the first port, the first and second annular rotating seal members and the axial opening of the base. In additional embodiment, the seal apparatus includes an outer shield defining a space between the outer shield and the body, the base and the first and second annular rotating seal members. Preferably the outer shield comprises a shield top, a shield bottom and a shield clamp, wherein the shield top is releasably mounted on the shield bottom, and wherein shield bottom and shield clamp have overlapping flanges which form a serpentine seal. In certain embodiments, the diameter of the shield bottom is smaller than the diameter of the shield clamp, the shield bottom has outwardly directed flange, and the shield clamp has an overlapping inwardly directed flange.
The seal apparatus also includes in certain embodiments an elastomeric spring element disposed between the shield top and the body, wherein the clamp is movable between a first position and a second position wherein the shield clamp is engaged with the base, wherein the spring element is compressed when the shield clamp is in the second position.
According to yet another aspect of the invention, a method for sealing a rotating processing container which rotates in a processing system is provided. The method includes providing a stationary seal member mounted on a processing system, the stationary seal having a plurality of circumferentially spaced annular sealing elements. The method also includes providing a rotating seal member mounted on the rotating processing container, the rotating seal member at least one annular sealing element. The sealing elements of the stationary seal member and the at least one sealing element of the rotating sealing member are contacted to form a rotating seal between the rotating processing container and the processing system.
According to another aspect of the invention, a method for sealing a rotating processing container is provided. The method includes providing a plurality of annular seals between the rotating processing container and a stationary portion of a processing system, wherein the plurality of annular seals define an annular space. The annular space is pressurized to provide an improved seal for the rotating processing container.
According to still another aspect of the invention, a method for heating or cooling a sample during transport of the sample into or out of a rotating processing container is provided. A seal apparatus including a rotating seal and a port for transport of a sample to the rotating processing container is provided, wherein the seal and the port define a space in contact with the port. The space between the seal and the port is filled with a material having a temperature which is at or below the temperature of the sample for cooling the sample, or a material having a temperature which is at or above the temperature of the sample for heating the sample. In preferred embodiments, the method provides for cooling of the sample by filling the space with waste materials generated by the processing methods, the waste materials being at or below room temperature. In certain embodiments the method provides cooling of the seal material during the transport of processing fluids into or out of the rotating processing container. The method includes providing a seal having an annular-shaped inlet/outlet port in fluid communication with the processing fluids, and filling the annular spaced with fluids that are cooler that the seal materials
In yet another aspect of the invention, a spring is provided. The spring includes a hollow elastomeric cylinder having bowed side portions. The spring can be constructed of a certain height, width, thickness and side portion arc to provide a constant biasing force upon compression of the spring. The compression of the spring concurrently changes the height, width and arc. In certain embodiments, the spring includes an elastomeric material of relatively thin cross-section which has a geometry that delivers a relatively constant force over a wide range of deflection values. Preferably the spring has a cross-sectional shape that includes bowed side walls.
Thus the invention provides a seal apparatus including a plurality of annular seals, and/or a seal apparatus including at least one annular seal and a pressurized annular space concentrically spaced apart from the annular seal. Methods of using the seal apparatuses for sealing rotating containers also are provided.
These and other aspects of the invention will be described in further detail in connection with the detailed description of the invention.